a. Field of Invention
This invention relates to the treatment of sewage whilst it is flowing through a sewer.
B. Description of Prior Art
It has for over fifty years been the established practice to conduct sewage through sewers to a treatment plant in which the sewage is contacted with micro-organisms which break down the offensive portions of the sewage to render it more fit for disposal. In order to keep alive the beneficial micro-organisms, aerobic conditions must be maintained in the sewage. This is usually achieved by aerating the sewage. One disadvantage of this method is that a prolonged treatment is required.
In order to reduce the time required for treatment, it has recently been proposed to oxygenate the sewage in the treatment plant. By this means higher levels of dissolved oxygen can be maintained in the sewage, whereby more rapid treatment is made possible. Often, however, large scale oxygenation plants are either expensive to install or operate. Moreover, such plants can do nothing to reduce the Biochemical Oxygen Demand of the incoming sewage. U.S. Pat. No. 3,607,735 discloses one such plant which has a tubular reactor in which the sewage is oxygenated.
Proposals for treating sewage within a sewer have been made. For example. U.S. Pat. No. 3,525,685 discloses introducing air or other gas into a sewer to prevent the formation of sulphides and to decrease the Biochemical Oxygen Demand of the sewage in the sewer. Our copending application Ser. No. 49,744 discloses an effective method and apparatus for treating sewage in a sewer by dissolving in sewage under pressure substantially all of an oxygenating gas introduced therein.